This Practice Note considers disclosure duties of a private prosecutor. It reviews the obligations on a private prosecutor under the Criminal Procedure and Investigations Act 1996 (CPIA 1996), as well as any common law duties, when these responsibilities arise, and what the responsibilities are at each stage of proceedings. It also outlines what consequences could flow from a failure to comply with these duties, the purpose and test for disclosure in the proceedings, and how the duties of disclosure on a private prosecutor diverge from those on a public prosecutor. It considers in detail the prosecutor’s duty of full and frank disclosure in relation to ex parte applications, as well as a private prosecutor’s responsibilities to pursue reasonable lines of enquiry and what this means in practice. It also covers privilege considerations and why legal professional privilege (LPP) considerations do not offer any protection to a private prosecutor in terms of their disclosure obligations, how this is different from a public prosecutor, and what practical steps private prosecutors can and should be taking to protect themselves from having to disclose privileged material. It also covers public interest immunity (PII) considerations for private prosecutors and provides tips for private prosecutors on the gathering, managing, documenting and storing of evidence and other material.